1. Field of the Invention
The present invention relates to an electronic circuit. More particularly, the present invention relates to a device for compensating for a variation of a resistance value dependent on a production process in an electronic circuit.
2. Description of the Related Art
In an Integrated Circuit (IC) design using a semiconductor manufacturing process, inactive elements such as capacitors, resistors and the like as well as active elements such as P-type Metal Oxide Semiconductors (PMOSs) and N-type Metal Oxide Semiconductors (NMOSs) inevitably have variations due to the semiconductor manufacturing process. Particularly, the resistors have a non-negligible, and possibly large, process variation. A general commercialized semiconductor manufacturing process produces resistors having a resistance value variation of about ±15% to ±25% or so in a range of ±3σ (σ: standard deviation) according to a stability of a resistor forming technology and the semiconductor manufacturing process.
A process variation of a resistor occurring in the semiconductor manufacturing process is non-negligibly large. FIG. 1 illustrates a process variation of a resistor according to the related art. In detail, FIG. 1 illustrates an example of a resistance value provided in a Complementary Metal Oxide Semiconductor (CMOS) process. In FIG. 1, an X axis denotes a standard deviation of a process variation. Typically, the process variation of the resistor follows a normal distribution. FIG. 1 shows a resistance value variation of +22.0% to −21.5% compared to a nominal value at a deviation level of ±3σ.
The process variation of the resistor greatly affects the performance of a circuit including the resistor. For example, a mixer may be affected by the process variation as is described below.
FIG. 2 illustrates an example of an up-conversion mixer circuit according to the related art.
In FIG. 2, a resistor R1 210 performs the following roles. First, the resistor R1 210 increases a high frequency characteristic of a circuit and guarantees a required bandwidth. Second, the resistor R1 210 guarantees a gain that is insensitive to a variation of transistors Q1 to Q6. Third, the resistor R1 210 controls a gain value and allows a circuit to have suitable linearity when an input signal has a large magnitude. Lastly, the resistor R1 210 allows the intact acceptance of a magnitude of an output signal of a block located ahead by increasing an input resistance value.
As described above, the resistor R1 210 of FIG. 2 has an important function in the mixer circuit. However, owing to a resistance value variation resulting from the manufacturing process, a gain of the mixer is not constant, as illustrated in FIG. 3.
FIG. 3 is a graph illustrating a gain variation of an up-conversion mixer according to the related art.
Referring to FIG. 3, the gain has a range of about 3.75 dB from the minimum gain to the maximum gain. In a case where the gain decreases, power at a final output terminal decreases as well, resulting in a decrease in a reception distance. In a case where the gain increases, linearity decreases making it difficult to guarantee a Signal to Noise Ratio (SNR). However, a variation of a resistance value is dominant over a variation of the gain, even if considering other elements and a variation of temperature and source voltage. As a result, a throughput decreases or a calibration for overcoming this decrease in linearity is required. This results in an increase of the unit cost of a circuit, an increase of power consumption, and an increase of a volume.
As described above, due to a variation of a resistance value dependent on a manufacturing process, there occurs a problem of circuit throughput degradation, power consumption increase and the like. Accordingly, even though there is a process variation of a resistor, an alternative for minimizing a damage resulting from this should be proposed.